Process for improved halide materials

ABSTRACT

Synthesizing a color stable Mn 4+  doped phosphor by contacting a gaseous fluorine-containing oxidizing agent with a precursor of: A a B b C c D d X x :Mn 4+ ; A ai B bi C ci D d X x Y d :Mn 4+ ; A 1   3 G 2−m−n Mn m Mg n Li 3 F 12 O p ; or AZF 4 :Mn 4+ . Where A is Li, Na, K, Rb, Cs, or a combination; B is Be, Mg, Ca, Sr, Ba, or a combination; C is Sc, Y, B, Al, Ga, In, Tl, or a combination; D is Ti, Zr, Hf, Rf, Si, Ge, Sn, Pb, or a combination; X is F or a combination of F and one of Br, Cl, and I; Y is O, or a combination of O and one of S and Se; A 1  is Na or K, or a combination; G is Al, B, Sc, Fe, Cr, Ti, In, or a combination; Z is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, In, or a combination.

BACKGROUND

Mn⁴+-complex fluoride phosphors offer potential advantages for highcolor rendering/gamut light sources that have high efficacies. However,the sensitivity of the materials to hydrolysis or photo-degradation maylimit their use in commercial products. Therefore, improvement in thestability of the materials is desirable.

BRIEF DESCRIPTION

Briefly, in one aspect, the present invention relates to a process forsynthesizing a color stable Mn⁴+ doped phosphor. A precursor of formulaI, II, III or IV is contacted with a fluorine-containing oxidizing agentin gaseous form at an elevated temperature to form the color stable Mn⁴⁺doped phosphor

A_(a)B_(b)C_(c)D_(d)X_(x):Mn⁴⁺  (I)

A_(ai)B_(bi)C_(ci)D_(d)X_(x)Y_(d):Mn⁴⁺  (II)

A¹ ₃G_(2−m−n)Mn_(m)Mg_(n)Li₃F₁₂O_(p),  (III)

AZF₄:Mn⁴⁺  (IV)

wherein

-   A is Li, Na, K, Rb, Cs, or a combination thereof;-   B is Be, Mg, Ca, Sr, Ba, or a combination thereof;-   C is Sc, Y, B, Al, Ga, In, Tl, or a combination thereof;-   D is Ti, Zr, Hf, Rf, Si, Ge, Sn, Pb, or a combination thereof;-   X is F or a combination of F and at least one of Br, Cl, and I;-   Y is O, or a combination of O and at least one of S and Se;-   A¹ is Na or K, or a combination thereof;-   G is Al, B, Sc, Fe, Cr Ti, In, or a combination thereof;-   Z is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc,    Y, In, or a combination thereof;-   0≤a<2;-   0≤b<1;-   0≤c<1;-   0≤d≤1;-   0.8≤ai≤1.2;-   0.8≤bi≤1.2;-   0≤ciii≤1.2;-   5.0≤x≤7;-   0.8≤c+d≤1.2;-   a+2b+3c+4d=x;-   0.8≤ci+d≤1;-   5.0≤x+d≤7.0;-   ai+2bi+3ci+4d=x+2d;-   0.02≤m≤0.2;-   0≤n≤0.4; and-   0≤p<1.

In another aspect, the present invention relates to color stable Mn⁴⁺doped phosphors that may be produced by the process, and lighting,backlighting light source and liquid crystal display apparatuses thatutilize the phosphors.

BRIEF DESCRIPTION OF DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic cross-sectional view of a lighting apparatus inaccordance with one embodiment of the invention;

FIG. 2 is a schematic cross-sectional view of a lighting apparatus inaccordance with another embodiment of the invention;

FIG. 3 is a schematic cross-sectional view of a lighting apparatus inaccordance with yet another embodiment of the invention;

FIG. 4 is a cutaway side perspective view of a lighting apparatus inaccordance with one embodiment of the invention;

FIG. 5 is a schematic perspective view of a surface-mounted device (SMD)backlight LED.

DETAILED DESCRIPTION

In the processes according to the present invention, a non-color stableprecursor to a color stable phosphor is annealed, or subjected to anelevated temperature, while in contact with an atmosphere containing afluorine-containing oxidizing agent. The non-color stable precursor hasa nominal composition that is the same as or very similar to the colorstable phosphor but it lacks the color stability of the final product.

The precursors of formula I are described in WO 2014/104143, assigned toMitsubishi Chemical Corporation

A_(a)B_(b)C_(c)D_(d)X_(x):Mn⁴⁺  (I)

wherein

-   A is Li, Na, K, Rb, Cs, or a combination thereof;-   B is Be, Mg, Ca, Sr, Ba, or a combination thereof;-   C is Sc, Y, B, Al, Ga, In, Tl, or a combination thereof;-   D is Ti, Zr, Hf, Rf, Si, Ge, Sn, Pb, or a combination thereof;-   X is F or a combination of F and at least one of Br, Cl, and I;-   0≤a <2;-   0≤b<1;-   0≤c<1;-   0≤d≤1;-   0.8≤c+d≤1.2;-   5.0≤x≤7; and-   a+2b+3c+4d=x.

Examples of the precursors of formula I include, but are not limited to,compounds of formula NaBaAlF₆:Mn⁴⁺, K₂SrAlF₆:Mn⁴⁺, and Na₂SrGaF₆:Mn⁴⁺.Additional examples and preparation of the compounds are disclosed in WO2014/104143.

The precursors of formula II are also described in WO 2014/104143

A_(aI)B_(bI)C_(cI)D_(d)X_(x)Y_(d):Mn⁴⁺  (II)

wherein

-   Y is O, or a combination of O and at least one of S and Se;-   0.8≤ai≤1.2-   0.8≤bi≤1.2-   0≤ci≤1.2-   0.8≤ci+di≤1-   5.0≤x+d≤7.0;-   ai+2bi+3ci+4d=x+2d; and-   Y is O, or a combination of O and at least one of S and Se.

Examples of the precursors of formula II include, but are not limitedto, compounds of formula NaBaTiF₅O andKCaAl_(0.5)Ti_(0.5)F_(5.5)O_(0.5). Additional examples and preparationof the compounds are disclosed in WO 2014/104143.

The precursors of formula I and II are described in WO 2014/104143 ashaving improved water resistance and reduced deterioration over time.However, annealing the materials according to the processes of thepresent invention may improve properties such as water resistance andlong term stability even further.

Precursors of formula III are described in US 2012/0305972, assigned toKoninklijke Philips Electronics N.V.

A¹ ₃G_(2−m−n)Mn_(m)Mg_(n)Li₃F₁₂O_(p),  (III)

wherein

-   A¹ is Na or K, or a combination thereof;-   G is Al, B, Sc, Fe, Cr, Ti, In, or a combination thereof;-   0.02≤m≤0.2,-   0≤n≤0.4; and-   0≤p<1.

An example of a precursor of formula IIINa₃Al_(1.94)Mn_(0.03)Mg_(0.03)Li₃F₁₂. Preparation of the precursors isdisclosed in US 2012/0305972.

Precursors of formula IV are described in CN 102827601, assigned toFujian Institute of Structure of Matter

AZF₄:Mn⁴⁺  (IV)

wherein

Z is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y,In, or a combination thereof.

An example of a precursor of formula IV is NaYF₄:Mn⁴⁺. Preparation ofthe precursors is disclosed in CN 102827601.

Although the inventors do not wish to be held to any particular theoryto explain the improvement in color stability that can result fromsubjecting the precursor to a process according to an embodiment of thepresent invention, it is postulated that the precursor may containdefects such as dislocations, F⁻ vacancies, cation vacancies, Mn³⁺ ions,Mn²⁺ ions, OH⁻ replacement of F⁻, or surface or interstitial H⁺/OH⁻groups that provide non-radiative recombination pathways, and these arehealed or removed by exposure to the oxidizing agent at elevatedtemperature.

The temperature at which the precursor is contacted with thefluorine-containing oxidizing agent may range from about 200° C. toabout 700° C., particularly from about 350° C. to about 600° C. duringcontact, and in some embodiments from about 200° C. to about 700° C. Invarious embodiments of the present invention, the temperature is atleast 100° C., particularly at least 225° C., and more particularly atleast 350° C. The phosphor precursor is contacted with the oxidizingagent for a period of time sufficient to convert it to a color stablephosphor. Time and temperature are interrelated, and may be adjustedtogether, for example, increasing time while reducing temperature, orincreasing temperature while reducing time. In particular embodiments,the time is at least one hour, particularly for at least four hours,more particularly at least six hours, and most particularly at leasteight hours. In a specific embodiment, the precursor is contacted withthe oxidizing agent for a period of at least eight hours and atemperature of at least 250° C., for example, at about 250° C. for aboutfour hours and then at a temperature of about 350° C. for about fourhours.

The fluorine-containing oxidizing agent may be F₂, HF, SF₆, BrF₅,NH₄HF₂, NH₄F, KF, AlF₃, SbF₅, ClF₃, BrF₃KrF, XeF₂, XeF₄, NF₃, SiF₄,PbF₂, ZnF₂, SnF₂, CdF₂ or a combination thereof. In particularembodiments, the fluorine-containing oxidizing agent is F₂. The amountof oxidizing agent in the atmosphere may be varied to obtain the colorstable phosphor, particularly in conjunction with variation of time andtemperature. Where the fluorine-containing oxidizing agent is F₂, theatmosphere may include at least 0.5% F₂, although a lower concentrationmay be effective in some embodiments. In particular the atmosphere mayinclude at least 5% F₂ and more particularly at least 20% F₂. Theatmosphere may additionally include nitrogen, helium, neon, argon,krypton, xenon, in any combination with the fluorine-containingoxidizing agent. In particular embodiments, the atmosphere is composedof about 20% F₂ and about 80% nitrogen.

The manner of contacting the precursor with the fluorine-containingoxidizing agent is not critical and may be accomplished in any waysufficient to convert the precursor to a color stable phosphor havingthe desired properties. In some embodiments, the chamber containing theprecursor may be dosed and then sealed such that an overpressuredevelops as the chamber is heated, and in others, the fluorine andnitrogen mixture is flowed throughout the anneal process ensuring a moreuniform pressure. In some embodiments, an additional dose of thefluorine-containing oxidizing agent may be introduced after a period oftime.

A lighting apparatus or light emitting assembly or lamp 10 according toone embodiment of the present invention is shown in FIG. 1. Lightingapparatus 10 includes a semiconductor radiation source, shown as lightemitting diode (LED) chip 12, and leads 14 electrically attached to theLED chip. The leads 14 may be thin wires supported by a thicker leadframe(s) 16 or the leads may be self supported electrodes and the leadframe may be omitted. The leads 14 provide current to LED chip 12 andthus cause it to emit radiation.

The lamp may include any semiconductor blue or UV light source that iscapable of producing white light when its emitted radiation is directedonto the phosphor. In one embodiment, the semiconductor light source isa blue emitting LED doped with various impurities. Thus, the LED maycomprise a semiconductor diode based on any suitable III-V, II-VI orIV-IV semiconductor layers and having an emission wavelength of about250 to 550 nm. In particular, the LED may contain at least onesemiconductor layer comprising GaN, ZnSe or SiC. For example, the LEDmay comprise a nitride compound semiconductor represented by the formulaIn_(i)Ga_(j)Al_(k)N (where 0≤i; 0≤j; 0≤k and I+j+k=1) having an emissionwavelength greater than about 250 nm and less than about 550 nm. Inparticular embodiments, the chip is a near-uv or blue emitting LEDhaving a peak emission wavelength from about 400 to about 500 nm. SuchLED semiconductors are known in the art. The radiation source isdescribed herein as an LED for convenience. However, as used herein, theterm is meant to encompass all semiconductor radiation sourcesincluding, e.g., semiconductor laser diodes. Further, although thegeneral discussion of the exemplary structures of the inventiondiscussed herein is directed toward inorganic LED based light sources,it should be understood that the LED chip may be replaced by anotherradiation source unless otherwise noted and that any reference tosemiconductor, semiconductor LED, or LED chip is merely representativeof any appropriate radiation source, including, but not limited to,organic light emitting diodes.

In lighting apparatus 10, phosphor composition 22 is radiationallycoupled to the LED chip 12. Radiationally coupled means that theelements are associated with each other so radiation from one istransmitted to the other. Phosphor composition 22 is deposited on theLED 12 by any appropriate method. For example, a water based suspensionof the phosphor(s) can be formed, and applied as a phosphor layer to theLED surface. In one such method, a silicone slurry in which the phosphorparticles are randomly suspended is placed around the LED. This methodis merely exemplary of possible positions of phosphor composition 22 andLED 12. Thus, phosphor composition 22 may be coated over or directly onthe light emitting surface of the LED chip 12 by coating and drying thephosphor suspension over the LED chip 12. In the case of asilicone-based suspension, the suspension is cured at an appropriatetemperature. Both the shell 18 and the encapsulant 20 should betransparent to allow white light 24 to be transmitted through thoseelements. Although not intended to be limiting, in some embodiments, themedian particle size of the phosphor composition ranges from about 1 toabout 50 microns, particularly from about 15 to about 35 microns.

In other embodiments, phosphor composition 22 is interspersed within theencapsulant material 20, instead of being formed directly on the LEDchip 12. The phosphor (in the form of a powder) may be interspersedwithin a single region of the encapsulant material 20 or throughout theentire volume of the encapsulant material. Blue light emitted by the LEDchip 12 mixes with the light emitted by phosphor composition 22, and themixed light appears as white light. If the phosphor is to beinterspersed within the material of encapsulant 20, then a phosphorpowder may be added to a polymer or silicone precursor, loaded aroundthe LED chip 12, and then the polymer precursor may be cured to solidifythe polymer or silicone material. Other known phosphor interspersionmethods may also be used, such as transfer loading.

In some embodiments, the encapsulant material 20 is a silicone matrixhaving an index of refraction R, and, in addition to phosphorcomposition 22, contains a diluent material having less than about 5%absorbance and index of refraction of R±0.1. The diluent material has anindex of refraction of ≤1.7, particularly ≤1.6, and more particularly≤1.5. In particular embodiments, the diluent material is of formula II,and has an index of refraction of about 1.4. Adding an opticallyinactive material to the phosphor/silicone mixture may produce a moregradual distribution of light flux through the phosphor/encapsulantmixture and can result in less damage to the phosphor. Suitablematerials for the diluent include fluoride compounds such as LiF, MgF₂,CaF₂, SrF₂, AlF₃, K₂NaAlF₆, KMgF₃, CaLiAlF₆, K₂LiAlF₆, and K₂SiF₆, whichhave index of refraction ranging from about 1.38 (AlF₃ and K₂NaAlF₆) toabout 1.43 (CaF₂), and polymers having index of refraction ranging fromabout 1.254 to about 1.7. Non-limiting examples of polymers suitable foruse as a diluent include polycarbonates, polyesters, nylons,polyetherimides, polyetherketones, and polymers derived from styrene,acrylate, methacrylate, vinyl, vinyl acetate, ethylene, propylene oxide,and ethylene oxide monomers, and copolymers thereof, includinghalogenated and unhalogenated derivatives. These polymer powders can bedirectly incorporated into silicone encapsulants before silicone curing.

In yet another embodiment, phosphor composition 22 is coated onto asurface of the shell 18, instead of being formed over the LED chip 12.The phosphor composition is in an embodiment coated on the insidesurface of the shell 18, although the phosphor may be coated on theoutside surface of the shell, if desired. Phosphor composition 22 may becoated on the entire surface of the shell or only a top portion of thesurface of the shell. The UV/blue light emitted by the LED chip 12 mixeswith the light emitted by phosphor composition 22, and the mixed lightappears as white light. Of course, the phosphor may be located in anytwo or all three locations or in any other suitable location, such asseparately from the shell or integrated into the LED.

FIG. 2 illustrates a second structure of the system according to anembodiment of the present invention. Corresponding numbers from FIGS.1-4 (e.g. 12 in FIGS. 1 and 112 in FIG. 2) relate to correspondingstructures in each of the figures, unless otherwise stated. Thestructure of the embodiment of FIG. 2 is similar to that of FIG. 1,except that the phosphor composition 122 is interspersed within theencapsulant material 120, instead of being formed directly on the LEDchip 112. The phosphor (in the form of a powder) may be interspersedwithin a single region of the encapsulant material or throughout theentire volume of the encapsulant material. Radiation (indicated by arrow126) emitted by the LED chip 112 mixes with the light emitted by thephosphor 122, and the mixed light appears as white light 124. If thephosphor is to be interspersed within the encapsulant material 120, thena phosphor powder may be added to a polymer precursor, and loaded aroundthe LED chip 112. The polymer or silicone precursor may then be cured tosolidify the polymer or silicone. Other known phosphor interspersionmethods may also be used, such as transfer molding.

FIG. 3 illustrates a third possible structure of the system according toan embodiment of the present invention. The structure of the embodimentshown in FIG. 3 is similar to that of FIG. 1, except that the phosphorcomposition 222 is coated onto a surface of the envelope 218, instead ofbeing formed over the LED chip 212. The phosphor composition 222 is inan embodiment coated on the inside surface of the envelope 218, althoughthe phosphor may be coated on the outside surface of the envelope, ifdesired. The phosphor composition 222 may be coated on the entiresurface of the envelope, or only a top portion of the surface of theenvelope. The radiation 226 emitted by the LED chip 212 mixes with thelight emitted by the phosphor composition 222, and the mixed lightappears as white light 224. Of course, the structures of FIGS. 1-3 maybe combined, and the phosphor may be located in any two or all threelocations, or in any other suitable location, such as separately fromthe envelope, or integrated into the LED.

In any of the above structures, the lamp may also include a plurality ofscattering particles (not shown), which are embedded in the encapsulantmaterial. The scattering particles may comprise, for example, alumina ortitania. The scattering particles effectively scatter the directionallight emitted from the LED chip, in an embodiment with a negligibleamount of absorption.

As shown in a fourth structure in FIG. 4, the LED chip 412 may bemounted in a reflective cup 430. The cup 430 may be made from or coatedwith a dielectric material, such as alumina, titania, or otherdielectric powders known in the art, or be coated by a reflective metal,such as aluminum or silver. The remainder of the structure of theembodiment of FIG. 4 is the same as those of any of the previousfigures, and can include two leads 416, a conducting wire 432, and anencapsulant material 420. The reflective cup 430 is supported by thefirst lead 416 and the conducting wire 432 is used to electricallyconnect the LED chip 412 with the second lead 416.

Another structure (particularly for backlight applications) is a surfacemounted device (“SMD”) type light emitting diode 550, e.g. asillustrated in FIG. 5. This SMD is a “side-emitting type” and has alight-emitting window 552 on a protruding portion of a light guidingmember 554. An SMD package may comprise an LED chip as defined above,and a phosphor material that is excited by the light emitted from theLED chip. In other embodiments, the LED lamp of FIGS. 1-4 may be used asa backlighting light source apparatus disposed on a back surface of aliquid crystal panel. Devices having a display including a semiconductorlight source; and a color stable Mn⁴⁺ doped phosphor include, but arenot limited to, TVs, computers, smartphones, tablet computers and otherhandheld devices.

When used with an LED emitting at from 350 to 550 nm and one or moreother appropriate phosphors, the resulting lighting system will producea light having a white color. Lamp 10 may also include scatteringparticles (not shown), which are embedded in the encapsulant material.The scattering particles may comprise, for example, alumina or titania.The scattering particles effectively scatter the directional lightemitted from the LED chip, in an embodiment with a negligible amount ofabsorption.

In addition to the color stable Mn⁴⁺ doped phosphor, phosphorcomposition 22 may include one or more other phosphors. When used in alighting apparatus in combination with a blue or near UV LED emittingradiation in the range of about 250 to 550 nm, the resultant lightemitted by the assembly will be a white light. Other phosphors such asgreen, blue, yellow, red, orange, or other color phosphors may be usedin the blend to customize the white color of the resulting light andproduce specific spectral power distributions. Quantum dots of anydesired color may also be used in phosphor composition 22, or may bedisposed in a layer separate from phosphor composition 22. Othermaterials suitable for use in phosphor compostion 22 includeelectroluminescent polymers such as polyfluorenes, in an embodimentpoly(9,9-dioctyl fluorene) and copolymers thereof, such aspoly(9,9′-dioctylfluorene-co-bis-N,N′-(4-butylphenyl)diphenylamine)(F8-TFB); poly(vinylcarbazole) and polyphenylenevinylene and theirderivatives. In addition, the light emitting layer may include a blue,yellow, orange, green or red phosphorescent dye or metal complex, or acombination thereof. Materials suitable for use as the phosphorescentdye include, but are not limited to, tris(1-phenylisoquinoline) iridium(III) (red dye), tris(2-phenylpyridine) iridium (green dye) and Iridium(III) bis(2-(4, 6-difluorephenyl)pyridinato-N,C2) (blue dye).Commercially available fluorescent and phosphorescent metal complexesfrom ADS (American Dyes Source, Inc.) may also be used. ADS green dyesinclude ADS060GE, ADS061GE, ADS063GE, and ADS066GE, ADS078GE, andADS090GE. ADS blue dyes include ADS064BE, ADS065BE, and ADS070BE. ADSred dyes include ADS067RE, ADS068RE, ADS069RE, ADS075RE, ADS076RE,ADS067RE, and ADS077RE.

Suitable phosphors for use in phosphor composition 22 include, but arenot limited to:

-   ((Sr_(1−z) (Ca, Ba, Mg, Zn)_(z))_(1−(x+w))(Li, Na, K,    Rb)_(w)(Ce_(x))₃(Al_(1−y)Si_(y))O_(4+y+3(x−w))F_(1−y−3(x−w)),    0<x≤0.10, 0≤y≤0.5, 0≤z≤0.5, 0≤w≤x;-   (Ca, Ce)₃Sc₂Si₃O₁₂ (CaSiG);-   (Sr,Ca,Ba)₃Al_(1−x)Si_(x)O_(4+x)F_(1−x):Ce³⁺ (SASOF));-   (Ba,Sr,Ca)₅(PO₄)₃(Cl,F,Br,OH):Eu²⁺,Mn²⁺; (Ba,Sr,Ca)BPO₅:Eu²⁺,Mn²⁺;-   (Sr,Ca)₁₀ (PO₄)₆*vB₂O₃:Eu²⁺(wherein 0<v≤1); Sr₂Si₃O₈*2SrCl₂:Eu²⁺;-   (Ca,Sr,Ba)₃MgSi₂O₈:Eu²⁺,Mn²⁺; BaAl₈O₁₃:Eu²⁺; 2SrO*0.    84P₂O₅*0.16B₂O₃:Eu²⁺;-   (Ba,Sr,Ca)MgAl₁₀O₁₇:Eu²+,Mn²+; (Ba,Sr,Ca)Al₂O₄:Eu²+;    (Y,Gd,Lu,Sc,La)BO₃:Ce³+,Tb³+;-   ZnS:Cu⁺,Cl⁻; ZnS:Cu⁺,Al³+; ZnS:Ag⁺,Cl⁻; ZnS:Ag⁺,Al³⁺;    (Ba,Sr,Ca)₂Si_(1−ξ)O_(4−2ξ):Eu²+(wherein 0≤ξ≤0.2);    (Ba,Sr,Ca)₂(Mg,Zn)Si₂O₇:Eu²⁺; (Sr,Ca,Ba)(Al,Ga,In)₂S₄:Eu²⁺;-   (Y,Gd,Tb,La,Sm,Pr,Lu)₃(Al,Ga)⁵⁻⁶⁰ O_(12−3/2α):Ce³⁺(wherein 0≤α≤0.5);-   (Ca,Sr)₈(Mg,Zn)(SiO₄)₄Cl₂:Eu²⁺,Mn²⁺; Na₂Gd₂B₂O₇:Ce³⁺,Tb³⁺;-   (Sr,Ca,Ba,Mg,Zn)₂P₂O₇:Eu²⁺,Mn²⁺; (Gd,Y,Lu,La)₂O₃:Eu³⁺,Bi³⁺;    (Gd,Y,Lu,La)₂O₂S:Eu³⁺,Bi³⁺;-   (Gd,Y,Lu,La)VO₄:Eu³⁺,Bi³⁺; (Ca,Sr)S:Eu²⁺,Ce³⁺; SrY₂S₄:Eu²⁺;    CaLa₂S₄:Ce³⁺;-   (Ba,Sr,Ca)MgP₂O₇:Eu²+,Mn²+; (Y,Lu)₂WO₆:Eu³+,Mo⁶+;    (Ba,Sr,Ca)_(β)Si_(γ)N_(μ):Eu²+ (wherein 2β+4γ=3μ);    Ca₃(SiO₄)Cl₂:Eu²⁺;    (Lu,Sc,Y,Tb)_(2−u−v)Ce_(v)Ca_(1+u)Li_(w)Mg_(2−w)P_(w)(Si,Ge)_(3−w)O_(12−u/2)    (where −0.5≤u≤1, 0<v≤0.1, and 0≤w≤0.2);    (Y,Lu,Gd)_(2−φ))Ca_(φ)Si₄N_(6+φ)C_(1−φ):Ce³⁺, (wherein 0≤φ≤0.5);-   (Lu,Ca,Li,Mg,Y), α-SiAlON doped with Eu²⁺ and/or Ce³⁺;    (Ca,Sr,Ba)SiO₂N₂:Eu²⁺,Ce³⁺; β-SiAlON:Eu²⁺, 3.5MgO*0.5MgF₂*GeO₂:Mn⁴⁺;    Ca_(1−c−f)Ce_(c)Eu_(f)Al_(1+c)Si_(1−c)N₃, (where 0≤c≤0.2, 0≤f≤0.2);-   Ca_(1−h−r)Ce_(h)Eu_(r)Al_(1−h)(Mg,Zn)_(h)SiN₃, (where 0≤h≤0.2,    0≤r≤0.2); Ca_(1−2s−t)Ce_(s)(Li,Na)_(s)Eu_(t)AlSiN₃, (where 0≤s≤0.2,    0≤f≤0.2, s+t>0); (Sr,Ca)AlSiN₃:Eu²⁺ and    Ca_(1−σ−χ−φ)Ce_(σ)(Li,Na)_(χ)Eu_(φ)Al_(1+σ−χ)Si_(1−σ+χ)N₃, (where    0≤σ≤0.2, 0≤χ≤0.4, 0≤φ≤0.2).

The ratio of each of the individual phosphors in the phosphor blend mayvary depending on the characteristics of the desired light output. Therelative proportions of the individual phosphors in the variousembodiment phosphor blends may be adjusted such that when theiremissions are blended and employed in an LED lighting device, there isproduced visible light of predetermined x and y values on the CIEchromaticity diagram. As stated, a white light is in an embodimentproduced. This white light may, for instance, may possess an x value inthe range of about 0.20 to about 0.55, and ay value in the range ofabout 0.20 to about 0.55. As stated, however, the exact identity andamounts of each phosphor in the phosphor composition can be variedaccording to the needs of the end user. For example, the material can beused for LEDs intended for liquid crystal display (LCD) backlighting. Inthis application, the LED color point would be appropriately tuned basedupon the desired white, red, green, and blue colors after passingthrough an LCD/color filter combination.

The color stable Mn⁴⁺ doped phosphors may be used in applications otherthan those described above. For example, the material may be used as aphosphor in a fluorescent lamp, in a cathode ray tube, in a plasmadisplay device or in a liquid crystal display (LCD). The material mayalso be used as a scintillator in an electromagnetic calorimeter, in agamma ray camera, in a computed tomography scanner or in a laser. Theseuses are merely exemplary and not limiting.

EXAMPLES Example 1

A sample of Na₂Ba_(0.5)AlF₆:Mn⁴⁺ is placed in a furnace chamber. Thefurnace chamber is evacuated using a mechanical pump and purged multipletimes with nitrogen and nitrogen, fluorine mixtures. After several pumpand purge cycles, the furnace chamber is filled with an atmospherecontaining 20% fluorine gas and 80% nitrogen gas to a pressure of aboutone atmosphere. The chamber is then heated to about 540° C. Afterholding for about twelve hours, the chamber is cooled to roomtemperature. The fluorine nitrogen mixture is evacuated, the chamber isfilled and purged several times with nitrogen to ensure the completeremoval of fluorine gas before opening the chamber.

Example 2

A sample of NaBaTiF₅O:Mn⁴+ is placed in a furnace chamber. The furnacechamber is evacuated using a mechanical pump and purged multiple timeswith nitrogen and nitrogen, fluorine mixtures. After several pump andpurge cycles, the furnace chamber is filled with an atmospherecontaining 20% fluorine gas and 80% nitrogen gas to a pressure of aboutone atmosphere. The chamber is then heated to about 500° C. Afterholding for about four hours, the chamber is cooled to room temperature.The fluorine nitrogen mixture is evacuated, the chamber is filled andpurged several times with nitrogen to ensure the complete removal offluorine gas before opening the chamber.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

This written description uses examples to disclose the invention,including the preferred embodiments, and also to enable any personskilled in the art to practice the invention, including making and usingany devices or systems and performing any incorporated methods. Thepatentable scope of the invention is defined by the claims, and mayinclude other examples that occur to those skilled in the art. Suchother examples are intended to be within the scope of the claims if theyhave structural elements that do not differ from the literal language ofthe claims, or if they include equivalent structural elements withinsubstantial differences from the literal languages of the claims.

1. A process for synthesizing a color stable Mn⁴⁺doped phosphor, theprocess comprising contacting a precursor of formula I, II, III or IVA_(a)B_(b)C_(c)D_(d)X_(x):Mn⁴⁺  (I)A_(ai)B_(bi)C_(ci)D_(d)X_(x)Y_(d):Mn⁴⁺  (II)A¹ ₃G_(2−m−n)Mn_(m)Mg_(n)Li₃F_(12−p)O_(p),  (III)AZF₄:Mn⁴⁺  (IV) with a fluorine-containing oxidizing agent in gaseousform at an elevated temperature to form the color stable Mn⁴⁺ dopedphosphor; wherein A is Li, Na, K, Rb, Cs, or a combination thereof; B isBe, Mg, Ca, Sr, Ba, or a combination thereof; C is Sc, Y, B, Al, Ga, In,TI, or a combination thereof; D is Ti, Zr, Hf, Rf, Si, Ge, Sn, Pb, or acombination thereof; X is F or a combination of F and at least one ofBr, Cl, and I; Y is O, or a combination of O and at least one of S andSe; A¹ is Na or K, or a combination thereof; G is Al, B, Sc, Fe, Cr, Ti,in, or a combination thereof; Z is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, In, or a combination thereof; 0≤a<2;0≤b<1; 0≤c<1; 0≤d≤1; 0.8≤ai≤1.2; 0.8≤bi≤1.2; 0≤ciii≤1.2; 5.0≤x≤7;0.8≤c+d≤1.2; a+2b+3c+4d=x; 0.8≤ci+d≤1; 5.0≤x+d≤7.0; ai+2bi+3ci+4d=x+2d;0.02≤m≤0.2; 0≤n≤0.4; and 0≤p<1.
 2. A process according to claim 1,wherein the precursor is of formula I.
 3. A process according to claim1, wherein the precursor is of formula II.
 4. A process according toclaim 1, wherein the precursor is of formula III.
 5. A process accordingto claim 1, wherein the precursor is of formula IV.
 6. A processaccording to claim 1, wherein X is F.
 7. A process according to claim 1,wherein Y is O.
 8. A process according to claim 1, wherein B is Ca, Sr,Ba, or a combination thereof.
 9. A process according to claim 1, whereinC is Al, Ga, or a combination thereof.
 10. A process according to claim1, wherein D is Si, Ge, Ti, or a combination thereof.
 11. A processaccording to claim 1, wherein the fluorine-containing oxidizing agent isF₂.
 12. A process according to claim 1, wherein the temperature rangesfrom about 200° C. to about 700° C.
 13. A color stable Mn⁴⁺ dopedphosphor prepared by a process according to claim
 1. 14. A lightingapparatus comprising a semiconductor light source; and color stable Mn⁴⁺doped phosphor prepared by a process according to claim
 1. 15. Abacklighting light source apparatus comprising a semiconductor lightsource; and color stable Mn⁴⁺ doped phosphor prepared by a processaccording to claim
 1. 16. A liquid crystal display apparatus comprising:a liquid crystal panel; and the backlighting light source apparatusaccording to claim 15 disposed on a back surface of the liquid crystalpanel.
 17. A process for synthesizing a color stable Mn⁴⁺doped phosphor,the process comprising contacting a precursor of formula I with afluorine-containing oxidizing agent in gaseous form at an elevatedtemperature to form the color stable Mn⁴⁺doped phosphorA_(a)B_(b)C_(c)D_(d)X_(x):Mn⁴⁺  (I) wherein A is Li, Na, K, Rb, Cs, or acombination thereof; B is Be, Mg, Ca, Sr, Ba, or a combination thereof;C is Sc, Y, B, Al, Ga, In, TI, or a combination thereof; D is Ti, Zr,Hf, Rf, Si, Ge, Sn, Pb, or a combination thereof; X is F or acombination of F and at least one of Br, Cl, and I; 0≤a <2; 0≤b<1;0≤c<1; 0≤d≤1; 0.8≤c+d≤1.2; 5.0≤x≤7; and a+2b+3c+4d=x.
 18. A process forsynthesizing a color stable Mn⁴⁺ doped phosphor, the process comprisingcontacting a precursor of formula II with a fluorine-containingoxidizing agent in gaseous form at an elevated temperature to form thecolor stable Mn⁴⁺ doped phosphorA_(aI)B_(bI)C_(cI)D_(d)X_(x)Y_(d):Mn⁴⁺  (II) wherein Y is O, or acombination of O and at least one of S and Se; 0.8≤ai≤1.2 0.8≤bi≤1.20≤ci≤1.2 0.8≤ci+di≤1 5.0≤x+d≤7.0; ai+2bi+3ci+4d=x+2d; and Y is O, or acombination of O and at least one of S and Se.
 19. A process forsynthesizing a color stable Mn⁴⁺ doped phosphor, the process comprisingcontacting a precursor of formula III with a fluorine-containingoxidizing agent in gaseous form at an elevated temperature to form thecolor stable Mn⁴⁺ doped phosphorA¹ ₃G_(2−m−n)Mn_(m)Mg_(n)Li₃F₁₂O_(p),  (III) wherein A¹ is Na or K, or acombination thereof; G is Al, B, Sc, Fe, Cr, Ti, In, or a combinationthereof; 0.02≤m≤0.2, 0≤n≤0.4; and 0≤p<1.
 20. A process for synthesizinga color stable Mn⁴⁺ doped phosphor, the process comprising contacting aprecursor of formula IV with a fluorine-containing oxidizing agent ingaseous form at an elevated temperature to form the color stable Mn⁴⁺doped phosphorAZF₄:Mn⁴⁺  (IV) wherein Z is La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho,Er, Tm, Yb, Lu, Sc, Y, In, or a combination thereof.